EXTENSION OF PERMED HAIR 133 1.0- 0.5 AF(t)/&F o F(t)/F o I i\• ! I I o 20 o I I RINSE TREATMENT TIMES I I I REOXlDATION I 0 2o 25 0 I I RINSE [rnin] Figure 3. Typical curve for the change of the normalized static force F(t)/F o and the normalized dynamic force AF(t)/AFo during reduction with 1 M thioglycolic acid at pH 9 for 20 minutes and subsequent reoxidation (1 M TA). Experimental points have been omitted for reasons of clarity. The difference between the dynamic and the static relative force for 1 M TA is zero or slightly negative. In the other systems the difference between AF(t2)/AF o and F(t2)/F o is between 10% and 20% and is not significantly different from the initial difference in hi 1.0- 0,5- AF(t)I AF o F(t)IF o [ REDUCTION I I REOXIDATION [ 0 • 0 20 0 , , , I ' I , I , I , I , I ' I I ' I , I , I 0 20 0 25 0 I H20 I I RINSE I I RINSE TREATMENT TlklES [mini Figure 4. Typical curve for the change of the normalized static force F(t)/F o and the normalized dynamic force AF(t)/AFo during reduction with ! M cysteine-hydrochloride at pH 8 for 40 minutes (1 M Cys-HCI) and subsequent reoxidation.

134 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS la.I LO 1.0- 0.5 ÷ ] REDUCTION ] 0 /+0 , [ , I ' I , I , ] • [ , [ , 20 0 H20 [ I RINSE REOXlDATION [ 0 20 25 0 I I RINSE TREATMENT TIMES [rnin] Figure 5. Typical curve for the change of the normalized static force F(t)/F o and the normalized dynamic force AF(t)/AF o during the reduction/reoxidation with 1 M sodium sulfite at pH 6.4 for 40 minutes (1 M sulfite). water (95% conf. limits). In all cases the difference increases during the first rinse and increases further with reoxidation. Only slight changes of the normalized forces are observed for the second rinse. Table I summarizes the final values for the relative static and dynamic forces and the values for the initial recovery, R o, and the initial set, So, calculated according to equa- tions 16 and 2 where, with respect to equation 15, Fr•/F o = F(t t4)/F o and AFro/AF o --= AF(t t4)/AF o. H20 H202 H20 REDUCTION 1. R I NSE REOXlDAT[ON 2. R I N 5E lOO 50 A BC D ABC D ABC D ABC D F(t•) AF(tl) F(t2) AF(t2) Fo •Fo Fo •Fo A BC D A BC D ABCD ABC D A BC D A BCD F(t3) AF(t3) F(tz,) AF(tz,) F(ttz,) AF(ttz,) Fo •Fo Fo •Fo Fo •Fo Figure 6. Relative static and dynamic forces at the end of each treatment step for various reducing agents (95% conf. limits). A: 0.3 M TA B' 1 M TA C: 1 M Cys-HCL D: 1 M sulfite.